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Atari 800XL Memory Faulty

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Hi Guys,

 

I'm finally getting around to repairing a defunct Atari 800XL - As far as i can tell only the memory is faulty.

 

My options seem to be to either de-solder the RAM chips from the motherboard and replace them (if I can find some suitable RAM chips), or to get a RAM upgrade that by-passes the onboard RAM, if I can find one which does not require a FREDDY chip (none on the motherboard...).

 

Bearing in mind I've not soldered (or de-soldered) antyhing in anger yet, what would you recommend, and is there anyone in the UK who can point me to a domestic source for the RAM chips?

 

Cheers All!

 

-Peter.

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Arcade suppliers might be the go. Commodore 64 uses the same chip type, so there's another potential source.

 

Or there's the RAM 320XL, but not sure if any more are being made. They have the option to replace internal RAM with memory from the plugin device.

 

Another option could be to use a SIMM or different type of RAM chip such as 4464 as used in XEGS, but they'd be untidy wire jobs.

 

Most 800XLs should have the RAM chips socketed. In that case, if you have a known good machine you could swap in a chip at a time to see which ones are bad.

 

There's also the chance that the RAM itself is fine and the fault is somewhere else within the memory selection logic.

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Would these chips do the job?

 

IDT# IDT61298SA15Y Static RAM 64Kx4 28-Pin SOJ

 

I can't find the speed on them anywhere but I assume they'd be "good enough" as sourcing something slower than an A8 needs would be nigh impossible now...

 

-Peter

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Would these chips do the job?

 

IDT# IDT61298SA15Y Static RAM 64Kx4 28-Pin SOJ

 

I can't find the speed on them anywhere but I assume they'd be "good enough" as sourcing something slower than an A8 needs would be nigh impossible now...

 

-Peter

You need DRAM, not SRAM, for a drop-in replacement. Each chip is a 64Kx1 DRAM, so you need 8 to have 64Kx8.

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Lots of old IBM XT/AT memory expansion boards used 64K chips or 256K chips. I have a board I yanked from an old PC that has probably 32+ chips on it that I'm keeping :)

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Old ISA graphics cards can be a good RAM source, but they used all variety of chips. I got some 4x64k from one and have some 256x1k form another.

 

But with the emergence of the "Retro PC" scene, it's probably cheaper to just source the chips from a supplier.

 

IIRC, you can use the 256x1k chips but need to tie the extra address line to ground.

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the kind of ram you need will be marked with 4164 or 41256. The 4164's are a drop in replacement, and the 41256's, you just need to solder a wire to all the pin 1's and tie it to ground (i commonly do this when repairing machines, as the 41256 altho is a bigger ram, can usually be found much cheaper then the 4164's)

 

Futurlec has them (among other places, may want to look locally first), scroll to the bottom of the page to where it says 'Video Memory'

 

 

sloopy.

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There is a web seller called grandata,they have the chips you are looking for, £1 each last time I bought some

 

I would also say that it is pretty rare to find a UK 800xl that is socketed.

Also I am sure that I just POP the 41256 chips in, no soldering of pin 1, did I do something wrong?

You are half way to a 256k RAM upgrade with these ic's

Edited by mimo

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I can confirm that PAL 800XL's are notorious for being direct soldered and not socketed. Out of the 6 that have been through my possesion only one was partial socketed.

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Same ratio as me then, 12 800xl and 2 socketed (guess which ones I am keeping !)

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but it only tests the stack... which if just a single chip is bad COMPLETELY, this would be fine, but if a chip has bit errors outside the stack, this wouldnt work, which is the more common situation...

 

either way, if the machine has Micron Technology dram's, i would replace them all, even if they were 'working fine'...

 

sloopy.

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Thanks to everyone for their replies.

 

The Bad news is that the 800XL in question has "disappeared"... My spouse said it "was broken wasn't it?" Hmm...

 

I guess the good news is that I've aquired a 130XE instead (which has 128k AND actually works...)

 

Cheers, All.

 

-Peter

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Thanks to everyone for their replies.

 

The Bad news is that the 800XL in question has "disappeared"... My spouse said it "was broken wasn't it?" Hmm...

 

I guess the good news is that I've aquired a 130XE instead (which has 128k AND actually works...)

 

Cheers, All.

 

-Peter

 

that is 'justifiable homicide' in my house ;')

 

 

tell her, its $50-60 for another one... $15, at most $25 to fix :')

 

sloopy.

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Crikey, I was thinking "Grounds for Divorce" - you're harsh, but fair, sloopy :)

 

Thanks to everyone for their replies.

 

The Bad news is that the 800XL in question has "disappeared"... My spouse said it "was broken wasn't it?" Hmm...

 

I guess the good news is that I've aquired a 130XE instead (which has 128k AND actually works...)

 

Cheers, All.

 

-Peter

 

that is 'justifiable homicide' in my house ;')

 

 

tell her, its $50-60 for another one... $15, at most $25 to fix :')

 

sloopy.

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Hi Guys,

 

Resurrecting an old post. Posts I've been able to find on this topic are getting old...

 

I have an Atari 800XL (mainly non-socketed) which had ram sockets and replacement (hungarian 4264) RAM fitted by the former owner.

 

I have been getting random ram errors for about 6 months now. The computer will work fine and run ram test no worries for a couple of hours and then starts glitching / crashing and mem test fails. Sometimes mem test runs through no problems and then fails on subsequent pass.

 

 

I havn't checked the soldering on the ram sockets and before I do that I want to get hold of some replacement RAM.

 

What I have learnt:

1) It seems 4164 RAM is what was originally used. I understand that the mT brand RAM is to be avoided.

 

2) My Atari has 4264 RAM currently fitted. Many recommendations recommend 4264 or 4164.

 

3) Indeed. I have an original 130XE motherboard and all the RAM is mT 4264-20 except the module in top right corner which is marked NEC 8504R0167 D4164C-15. I have read this is a common RAM chip configuration for 130XE's - possibly because the first chip position was the most likely to fail, so Atari simply used more reliable NEC chips in the first position. I can't pull these chips for testing on my 800XL because they are soldered and I haven't tested or had the 130xe board running yet.

 

4) Futurlec is no longer selling 4164 or 4264 RAM - I have just had a 3 month old order cancelled and refunded.

 

Questions:

1) Could poor RAM socket soldering be the cause of my random RAM errors? Or is the (Hungarian) replacement RAM installed by the previous owner more likely to be the culprit?

 

2) Does it matter whether I use 4164 or 4264 RAM? I don't want to make motherboard modifications to accommodate non-spec RAM as once I have RAM sorted I want to install Lotharek's U1MB upgrade.

 

3) Where is the best place to purchase replacement RAM at a reasonable cost?

 

4) what are best RAMs to use for reliability (and the required timing)?

 

Cheers and sorry if I have overlooked the answers to these questions.

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Hi

 

Regarding point #3

 

Here is a place selling TI 4164's ( listed for C64 but would imagine they work in A8 ) @ £1.20 each ( He ships to USA so imagine he will send to New Zealand )

 

https://www.retroleum.co.uk/c64-chips

 

I have some Hitachi 4864's which are pin compatible with 4164's ( they aren't for sale btw ) - So if you find some 4864's they should work too.

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I have used NOS TI 4164's that I purchased off ebay in bulk on several 8-bits that I repaired and they work great!

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Hi

 

Regarding point #3

 

Here is a place selling TI 4164's ( listed for C64 but would imagine they work in A8 ) @ £1.20 each ( He ships to USA so imagine he will send to New Zealand )

 

https://www.retroleum.co.uk/c64-chips

 

I have some Hitachi 4864's which are pin compatible with 4164's ( they aren't for sale btw ) - So if you find some 4864's they should work too.

 

Thanks for this Vyper68. I have gone ahead and ordered 10 (8 plus 2 spareTI 4164's and will try them out. I'll report back when they've arrived and been fitted.

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I have used NOS TI 4164's that I purchased off ebay in bulk on several 8-bits that I repaired and they work great!

 

"NOS TI 4164's" I'm not sure what NOS means. Are these the same as the TI Rams that Vyper68 referred me to?

 

This is what the Retroleum.co.uk listing for the RAM I ordered says:

 

4164 RAM Chip - Texas Instruments Brand
  • Organization: 64K x 1, Speed: 150ns or faster, Package: 16 pin DIL
  • Unused, clean, old stock parts (condition as new - all chips tested before dispatch)
  • Texas Instruments brand.

This chip will replace:

  • Upper RAM chips in the ZX Spectrum 48K (Replaces TMS4532-15NL3, TMS4532-15NL4 , OKI M3732H-20 etc)*
  • Spectrum 128 RAM chip (RAM in 'toast rack' 128k and in early 128 +2s)
  • Commodore 64 RAM chips (most 'breadbin' models use 8 RAM chips. Note: The 64C uses 2 x 41464)

* These 4164 chips serve as a universal replacement for all the different types of UPPER RAM chips originally used in the Spectrum 48K - IE: You can use these to replace any number of bad chips at IC15-IC22 no matter what type of chips were originally installed (and the configuration links can be left alone). Please note: These chips cannot be (directly) used to replace the "4116" chips used for the LOWER 16KB of RAM in the bottom left of the Spectrum 48 PCB.

Faulty RAM chips in the C64 often result in an "Out of Memory" error on boot or less than 38911 bytes free. In the Spectrum, when the upper RAM is bad the system will often boot faster and work as a 16K machine. One crude but often effective way to test which chip is bad, is to "piggy-back" a working chip on each RAM chip one at a time. If the error goes away or at least changes, there's a good chance that chip is faulty.

I presume that Speed: "150ns or faster" means the RAM switches state in 150ns or under. Hopefully this is quick enough for the Atari...

Anyhow, Retroleum is showing 30 units still in stock, so assuming they work, the price @ £ 1.20 is definitely good! (fair shipping prices too).

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